Evaporator for refrigerating machine and refrigeration apparatus

ABSTRACT

An evaporator for a refrigerating system which prevents droplets of refrigerant from blowing upwards, and a refrigeration apparatus using thereof are provided. The evaporator for a refrigerating system includes a container into which the refrigerant is introduced, and heat exchanger tubes disposed in the container through which a cooled object flows. The evaporator further includes a prevention plate disposed above the heat exchanger tubes so that droplets of the refrigerant, which are blown upwards due to a boiling of the refrigerant, hit the prevention plate.

TECHNICAL FIELD

[0001] The present invention relates to an evaporator for arefrigerating system which refrigerates an object to be cooled (e.g.,water, brine, etc.) by exchanging heat between the object and therefrigerant, and a refrigeration apparatus using the evaporator.

Background Art

[0002] In a structure of large scale, such as a tall building, coolwater, which has been chilled by a refrigerating system, is circulatedthrough a pipe arrangement disposed in the structure so that heat isexchanged between the cool water circulating in the pipe arrangement andair present in the spaces of the structure to decrease the temperatureof the spaces.

[0003]FIG. 8 is a diagram showing an example of a conventionalevaporator which may be provided with a refrigerator. In thisevaporator, a plurality of bundles of heat exchanger tubes 2 throughwhich water passes is disposed in a staggered form in a cylindricalcontainer 1 into which a refrigerant is introduced.

[0004] The plurality of heat exchanger tubes 2 may be divided into twogroups, namely, a group of entering tubes which communicate with a waterentrance 3 and a group of exiting tubes which communicate with a waterexit 4. Water enters from the water entrance 3, passes through heatexchanger tubes 2 of the entering tube group in the container 1 to reacha water chamber (not shown in the figure), and then passes through theheat exchanger tubes 2 of the exiting tube group to exit from the waterexit 4. During this process, water is cooled down by heat exchange withthe refrigerant introduced into the container 1, and the refrigerantwhich received heat from the water, in turn, boils and vaporizes.

[0005] The vaporized refrigerant is then compressed in a compressor,which is not shown in the figure, and transferred to a condenser.

[0006] In the above-mentioned type of evaporator, however, when therefrigerant is boiled around the heat exchanger tubes 2 and vapor isgenerated, droplets of the refrigerant are often blown upwards by theforce of the refrigerant vapor. Then, some of these droplets ofrefrigerant are sometimes drawn into the above-mentioned compressor andcause problems, such as a decrease in the performance of the compressoror damage to an impeller.

[0007] Although attempts have been made to create open passages (i.e.,spaces among heat exchanger tubes) along the bundle of the heatexchanger tubes in an up-and-down direction as pathways for bubblesgenerated when the refrigerant boils, the force of the refrigerant vaporblown upwards from the opening of the passages is increased in thiscase.

[0008] Accordingly, one of the objects of the present invention is toprovide an evaporator for a refrigerating system, which is capable ofpreventing blown upwards of droplets of the refrigerant, and arefrigeration apparatus using the evaporator.

DISCLOSURE OF INVENTION

[0009] The present invention provides an evaporator for a refrigeratingsystem including a container into which a refrigerant is introduced, andheat exchanger tubes disposed in the container through which an objectto be cooled down flows, comprising: a prevention plate disposed abovethe heat exchanger tubes so that droplets of the refrigerant, which areblown upwards due to boiling of the refrigerant, hit the preventionplate and are prevented from proceeding beyond the prevention plate.

[0010] In accordance with another aspect of the invention, the heatexchanger tubes are divided into a plurality of vertically spaced groupsso that a space is formed between the groups of the heat exchanger tubesin vertical direction; and the prevention plate is disposed above thespace.

[0011] In yet another aspect of the invention, the distance between theprevention plate and the heat exchanger tubes at an uppermost level isabout 0.5 to 2 times the diameter of a heat exchanger tube which islocated at the uppermost level.

[0012] In yet another aspect of the invention, the prevention plate hasa cross section shaped like an inverted letter “V”, “U”, “W”, etc., andthe angle of the prevention plate is designed to be between about 60°and 120°.

[0013] In yet another aspect of the invention, an end portion of theprevention plate covers at least a part, preferably, half or all, of aheat exchanger tube which is located at the uppermost level of the heatexchanger tubes and is adjacent to the prevention plate.

[0014] In yet another aspect of the invention, a group of the heatexchanger tubes facing an inner surface of the container is disposed sothat a space is formed between the group of the heat exchanger tubes andthe container along the inner surface of the container; and a preventionplate is disposed above the space.

[0015] The present invention also provides a refrigeration apparatus,comprising: a compressor for compressing a refrigerant; a condenser forcondensing and liquefying the refrigerant which is compressed in thecompressor; a throttling mechanism for reducing the pressure of theliquefied refrigerant; and an evaporator for cooling down an object tobe cooled by exchanging heat between the object to be cooled and aresultant condensed and pressure-reduced liquefied refrigerant, andevaporating and vaporizing the liquefied refrigerant, wherein theevaporator is one of the above-mentioned evaporators.

BRIEF DESCRIPTION OF DRAWINGS

[0016]FIG. 1 is a diagram showing a schematic structure of arefrigerating system to which an evaporator according to an embodimentof the present invention may be applied.

[0017]FIG. 2 is a diagram showing a cross-sectional view of therefrigerating system shown in FIG. 1 cut along the II - II line.

[0018]FIG. 3 is a diagram showing a partial enlarged cross-sectionalview of the arrangement of a prevention plate having a cross sectionsubstantially shaped as an inverted letter “V”.

[0019]FIG. 4 is a diagram showing a partial enlarged cross-sectionalview of the arrangement of a flat prevention plate.

[0020]FIG. 5 is a diagram showing a partial enlarged cross-sectionalview of the arrangement of a plurality of the prevention plates.

[0021]FIG. 6 is a perspective view to explain the structure andconstruction of an evaporator in a refrigeration apparatus according toan embodiment of the present invention.

[0022]FIG. 7 is a schematic piping diagram to explain the configurationof the evaporator in the refrigeration apparatus according to anembodiment of the present invention.

[0023]FIG. 8 is a diagram showing an example of a conventionalevaporator which may be provided with a refrigerator.

BEST MODE FOR CARRYING OUT THE INVENTION

[0024] The evaporator for a refrigerating system according toembodiments of the present invention will be described with reference tothe accompanying drawings.

[0025]FIG. 1 is a diagram showing a schematic structure of arefrigerating system according to an embodiment of the presentinvention. The refrigerating system includes a condenser 10, anexpansion valve (throttle valve) 11, an evaporator 12, and a compressor13. The condenser 10 condenses and liquefies a refrigerant by exchangingheat between cooling water (the cooled object) and the refrigerant whichmay be in a vapor phase. The expansion valve 11 decreases the pressureof the condensed refrigerant. The evaporator 12 refrigerates the coolingwater by exchanging heat between the cooling water and the condensedrefrigerant. The compressor 13 compresses the refrigerant, which hasbeen evaporated and vaporized in the evaporator 12, and supplies it tothe above-mentioned condenser 10. The cooling water refrigerated in theevaporator 12 may be utilized, for instance, for air-conditioning in abuilding.

[0026]FIG. 2 is a diagram showing a cross-sectional view of therefrigerating system shown in FIG. 1 cut along the II - II lineindicated by arrows. As shown in FIG. 2, the evaporator 12 includes acylindrical container 14 into which a refrigerant is introduced, and aplurality of bundles of heat exchanger tubes 15 disposed in thecontainer 14.

[0027] The plurality of heat exchanger tubes 15 is disposed in thelongitudinal direction (i.e., a vertical direction with respect to thesheet surface of FIG. 2) of the container 14 and function as pathwaysfor cooling water, which is the cooled object. The heat exchanger tubes15 are divided into groups, namely, a group of entering tubes whichcommunicate with a cooling water entrance 16 a and a group of exitingtubes which communicate with a cooling water exit 16 b shown in FIG. 1.The direction of the flow of cooling water in the heat exchanger tubes15 communicating with the cooling water entrance 16 a is different fromthe direction of the flow of cooling water in the heat exchanger tubes15 communicating with the cooling water exit 16 b.

[0028] The plurality of heat exchanger tubes 15 may be divided into aplurality of groups, for instance, four, (i.e., groups of tubes A-D asshown in FIG. 2) in the lower half of the container 14. A space 17 isformed between each of the groups A-D of the heat exchanger tubes 15 ina vertical direction, and a space 18 is formed between the group A andthe container 14 along the inner surface of the container 14, andbetween the group D and the container 14 along the inner surface of thecontainer 14. Note that the above-mentioned spaces 17 and 18 arehereinafter referred to as passages 17 and 18 since it may be regardedthat they are formed by extracting the corresponding heat exchangertubes 15 which may be present there originally.

[0029] A prevention plate 19 having an inverted “V” cross sectionalshape is disposed above each of the passage 17. Also, a blow-upprevention plate 20, which may have a flat shape, is disposed above eachof the passage 18. The shape of the prevention plates 19 and 20 is notparticularly limited, and any suitable shape, such as inverted “U” and“W”, can be used.

[0030] As shown in the enlarged view of FIG. 3, the vertical angle θ ofthe prevention plate 19 in this embodiment is designed to be betweenabout 60° and 120°. The prevention plate 19 is disposed at a positionabove the passage 17 so that the right and left portions, respectively,of the prevention plate 19 cover at least a part, preferably, half orall, of the corresponding adjacent heat exchanger tube 15 at theuppermost level, and that the distance between the right and left edgeportions, respectively, of the prevention plate 19 and the correspondingheat exchanger tube 15 be 0.5 to 2 times the diameter D of the heatexchanger tube 15.

[0031] On the other hand, as shown in the enlarged view of FIG. 4, theprevention plate 20 is disposed above the heat exchanger tube 15 so thatthe edge portion thereof covers at least a part of the correspondingadjacent heat exchanger tube 15 at the uppermost level, and that thedistance between the edge portion of the prevention plate 19 and thecorresponding heat exchanger tube 15 be 0.5 to 2 times the diameter D ofthe heat exchanger tube 15.

[0032] Note that although the end portion of the prevention plate 20 isdownwardly bent in order to stop the upward flow from the passage 18 inthe above embodiment, the prevention plate 20 may have a flat shape andno problems would be caused by the use of such a prevention plate 20.

[0033] The number of the heat exchanger tubes 15 contained in the groupsA-D in the above embodiment may be chosen to be, for instance, fivehundreds. Also, the heat exchanger tubes 15 in each of the groups A-Dmay be arranged in a staggered manner. That is, the heat exchanger tubes15 at an upper level are shifted by about half of the distance, i.e., ½offset, between each other in the transverse direction with respect tothe heat exchanger tubes 15 at the next lower level.

[0034] In the evaporator 12 having the above-mentioned configuration,the refrigerant is introduced into the container 14 via a lower portionthereof. Since the refrigerant boils when heat is exchanged betweencooling water flowing through the heat exchanger tubes 15 and itself,vapor of the refrigerant is generated around the heat exchanger tubes15, which are mainly located at a lower portion of each of the groupsA-D, and rises to the surface through the passages 17 or 18.

[0035] Although the vapor and droplets of refrigerant bubbles upvigorously from the opening of the passages 17, the ascent rate thereofis significantly reduced when the vapor and droplets hit theabove-mentioned prevention plates 19 and 20.

[0036] As a result, only the vapor of the evaporated refrigerant exitsthe container 14 via the demister 21. That is, it becomes possible toprevent the droplets of refrigerant from being supplied to thecompressor 13 shown in FIG. 1. Note that the above-mentioned vapor ofthe refrigerant is supplied to the compressor 13 and is compressed.

[0037] As mentioned above, according to the evaporator of thisembodiment of the present invention, since the prevention plates 19 and20 prevent the droplets of refrigerant being blown upwards beyond theplates 19 and 20 in the container 14, the droplets of refrigerant arenot drawn into the compressor 13. Accordingly, it becomes possible toavoid problems, such as a decrease in the performance of the compressoror damage to an impeller.

[0038] Note that although the prevention plates 19 and 20 are disposedonly above the passages 17 and 18 in the above-mentioned embodiments,droplets of refrigerant may sometimes be blown upwards by bubbles of therefrigerant which ascend between the heat exchanger tubes 15 in each ofthe groups A-D. Accordingly, the prevention plates 19 may be disposed soas to cover all of the heat exchanger tubes 15 of the groups A-D asshown in FIG. 5. In this manner, it becomes possible to assuredlyprevent the droplets of refrigerant from entering the compressor 13.

[0039] In this embodiment, although each of the prevention plates 19 isdisposed so as to be vertically shifted relative to each other and tooverlap, when viewed from the above, with adjacent prevention plates 19,it is possible to arrange the prevention plates 19 in a differentmanner.

[0040] Also, although the passages 17 and 18 are provided in order todecrease the amount of bubbles in each of the tube groups A-D in theevaporator 12 according the above-mentioned embodiments, the presentinvention, which can prevent the droplets of refrigerant from blowingupwards, may also be effectively and suitably applied to an evaporatorhaving no passages 17 and 18.

[0041] The heat exchanger tubes 15 are arranged in the staggered mannerin each of the groups A-D in the above-mentioned embodiments to enhancethe contact between the refrigerant and the heat exchanger tubes 15 andto improve the heat transfer rate between them.

[0042] Next, the overall structure of a refrigeration apparatusincluding the above-mentioned evaporator according to an embodiment ofthe present invention will be explained with reference to FIGS. 6 and 7.

[0043] The refrigeration apparatus shown in the figures includes theabove-mentioned evaporator 12; a compressor 13 for compressing therefrigerant vaporized in the evaporator 12; a condenser 10 forcondensing and liquefying the refrigerant compressed in the compressor13; an expansion valve (throttle valve) 11 for reducing the pressure ofthe refrigerant liquefied in the condenser 10; an intermediate cooler 25for temporarily storing and cooling the refrigerant liquefied in thecondenser 10; and an oil cooler 26 for cooling the lubricating oil forthe compressor 13 by utilizing a portion of the refrigerant cooled inthe condenser 13.

[0044] Also, a motor (a driving mechanism) 27 is connected to thecompressor 13 for operating the compressor 13.

[0045] The condenser 10, the throttle valve 11, the evaporator 12, thecompressor 13, and the intermediate cooler 25 are connected via primarypiping 28 to constitute a closed system in which the refrigerant iscirculated.

[0046] The compressor 13 in this embodiment is based on a 2-stage(multistage) centrifugal compressor, a so-called turbo compressor, andthis turbo compressor 13 is provided with a plurality of impellers 29.The refrigerant is compressed in a first stage impeller 29 a situated inthe upstream side of the impeller 29, and the compressed refrigerant isled into the second stage impeller 29 b to be compressed further andthen sent to the condenser 10.

[0047] The condenser 10 includes a main condenser 10 a and a sub-cooler10 b which is an auxiliary compressor, and the refrigerant is introducedfirst into the main condenser 10 a and then to the sub-cooler 10 b.However, a portion of the refrigerant cooled in the main condenser 10 ais introduced into the oil cooler 26, without passing through thesub-cooler 10 b, to cool the lubricating oil.

[0048] Also, apart from the above process, a portion of the refrigerantcooled in the main condenser 10 a is introduced into the casing 31 ofthe motor 27, which will be explained later, without passing through thesub-cooler 10 b, and cools stators and coils which are not shown in thediagram.

[0049] The throttle valve 11 is disposed between the condenser 10 andthe intermediate cooler 25, and between the intermediate cooler 25 andthe evaporator 12, and they are used for stepwise reduction of thepressure of the refrigerant liquefied in the condenser 10.

[0050] The structure of the intermediate cooler 25 is equivalent to ahollow vessel, and the refrigerant which has been cooled in the maincondenser 10 a and the sub-cooler 10 b and reduced in pressure in thethrottle valve 11, is temporarily stored therein and is subjected tofurther cooling. Here, the vapor phase components in the intermediatecooler 25 are introduced into the second stage impeller 29 b of thecompressor 13 through the bypass piping 23, without passing through theevaporator 12.

Industrial Applicability

[0051] According to the evaporator of the present invention, since theprevention plates are disposed above the heat exchanger tubes so thatdroplets of refrigerant, which are blown upwards when the refrigerant isboiled, hit the prevention plates, the droplets of refrigerant are notdrawn into the compressor. Accordingly, it becomes possible to avoidproblems caused by the droplets, such as a decrease in the performanceof the compressor or damage to an impeller.

1. An evaporator for a refrigerating system including a container intowhich a refrigerant is introduced, and heat exchanger tubes disposed inthe container through which an object to be cooled down flows,comprising: a prevention plate disposed above said heat exchanger tubesso that droplets of the refrigerant, which are blown upwards due toboiling of the refrigerant, hit said prevention plate.
 2. An evaporatorfor a refrigerating system according to claim 1, wherein said heatexchanger tubes are divided into a plurality of vertically spaced groupsso that a space is formed between the groups of said heat exchangertubes in a vertical direction; and said prevention plate is disposedabove the space.
 3. An evaporator for a refrigerating system accordingto claim 1, wherein the distance between said prevention plate and saidheat exchanger tubes at an uppermost level is about 0.5 to 2 times thediameter of a heat exchanger tube which is located at the uppermostlevel.
 4. An evaporator for a refrigerating system according to claim 1,wherein said prevention plate has a cross section substantially shapedas an inverted letter “V”, and a vertical angle of said prevention plateis designed to be between 60° and 120°.
 5. An evaporator for arefrigerating system according to claim 1, wherein an end portion ofsaid prevention plate covers at least a part of a heat exchanger tubewhich is located at the uppermost level of said heat exchanger tubes andis adjacent to said prevention plate.
 6. An evaporator for arefrigerating system according to claim 1, wherein a group of said heatexchanger tubes facing an inner surface of said container is disposed sothat a space is formed between the group of said heat exchanger tubesand said container along the inner surface of said container; and saidprevention plate is disposed above said space.
 7. A refrigerationapparatus, comprising: a compressor for compressing a refrigerant; acondenser for condensing and liquefying the refrigerant which iscompressed in said compressor; a throttling mechanism for reducing thepressure of the liquefied refrigerant; and an evaporator for coolingdown an object to be cooled by exchanging heat between the object to becooled and a resultant condensed and pressure-reduced liquefiedrefrigerant, and evaporating and vaporizing the liquefied refrigerant,wherein said evaporator is the one as set forth in any one of claims1-6.